Electrical protective device.



L.' M. PERKINS. ELECTRICAL PROTECTIVE DEVICE.

APPLICATION FILED OCT. 30. I916.

Patented May 1, 1917.

INVENTOR L aarence A Per/rm s.

ATTORNEY UNITED STATES PATENT OFFICE.

LAURENCE M. PERKINS, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR T0 WESTING-HOUSE ELEC'IRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYL-VANIA.

ELECTRICAL PROTECTIVE DEVICE.

Application filed October 30, 1916.

To all whom it may concern:

Be it known that I, Lannnnon M. PER- KINS, a citizen of the UnitedStates, and a resident of IVilkinsburg, in the county of Allegheny andState of Pennsylvania, have invented a new and useful Improvement inElectrical Protective Devices, of which the following is aspecification.

My invention relates to electrical protective devices and particularlyto means for protecting electrical translating devices in accordancewith the temperatures thereof.

The object of my invention is to provide a device of the above-indicatedcharacter that shall operate when the difference in the energy loss in aportion of the translating device that is to be protected and the energyloss in a resistor, that normally bears a predetermined relation to theenergy loss in the translating device, exceeds a predetermined value.

In the carrying out of my invention, I connect a resistor having asubstantially constant resistance to a portion of a translating devicethat is to be protected, and I so connect an electro-responsive deviceor a relay to. the resistor and the translating device that it isactuated in accordance with the relative difference in the energy lossin the resistor and a portion of the translating device. That is, therelay will operate backwardly so long as the ratio of the losses in thetranslating device and the resistor is below a predetermined value; willremain stationary when the ratio of the losses is a predetermined valueand will operate to trip a circuit interrupter, control a signal deviceor indicate the temperature of the translating device when its load sochanges I that the ratio of its energy loss to the energy loss in theresistor exceeds a predetermined value.

Figure 1 of the accompanying drawings is a diagrammatic view of aprotective device embodying my invention, and Fig. 2 is a diagrammaticview of a modified form of the protective device embodying my invention.

In Fig. 1 of the drawings, a relay 1 is provided for controlling thetripping of a circuit interrupter 2 when the temperature of afield-magnet winding 8, or other translating device, reaches apredetermined value.

A circuit 4, comprising a resistor 5, a reactor fiend a an fo m r Windng 'Z, i

Specification of Letters Patent.

Patented. May 1, 1917.

Serial No. 128,414.

a substantially constant resistance of suchvalue that the energy lossesin the circuit 4:

and in the winding 3 will be the same or have a constant ratio underpredetermined conditions. That is, the resistor 5 is so proportionedthat the energy loss therein is equal or proportional to the energy lossin the winding 3 at a predetermined temperature. However, since theresistance of the resistor is adapted to be constant under allconditions of temperature, when an excessive load traverses the winding3, its resistance will increase and its energy loss will be relativelygreater than the energy loss in the circuit l.

A transformer winding 8 is so connected to the winding 3 that currentproportional to the current traversing the winding 3 traverses the same.The transformer windings T and 8. are wound on a common magnetizablecore member 7 and are so con nected that they oppose each other. Awinding 8 is also wound. on the core member 7 and is connected to thewinding 9 of the relay 1 for the purpose of supplying the same withcurrent proportional to the difference in the currents traversing thewindings 7 and S. A winding 10; of the relay 1 is operatively connectedacross the terminals of the winding 3 and the circuit t. Thus, thearmaturel l of the relay 1 will developv a torque that is proportionalto the relative difference between the energy consumed in the winding 3and the circuit 4:.

W hen a relatively smallcurrent traverses the winding 3, the armature 11will turn in a counter-clockwise direction until its movable contactmember 12 engages a stationary stop 13. At a predetermined value 0t current, traversing the winding 3, the ratio of the currents traversing thewinding 3 and the circuit t will be such as to cause the armature 11 toremain stationary, and, when a relatively large amount of currenttraverses the Winding 3, the armature 11 will turn, in a clockwisedirection, tocause its movable contact member 12 to engage a stationarycontact member 14:. The contact members 12 and let constitute theseparable terminals of a circuit 15 comprising a source 16 ofelectromotive force and the winding 17 of a tripping electromagnet 18.Thus, when the temperature of the winding 3 reaches a adapted tocooperate with a scale 12 for thepurpose of indicating, betweenpredetermined limits, the temperature of the device 3.

In Fig. 2 of the drawings, a transformer 19, having a primary winding 20and a secondary winding 21, is adapted to be protected by a circuitinterrupter 22 that is controlled by a relay 23.

The relay 23 comprises a magnetizable core member 24, windings 25 and26, an armature 27 and movable and stationary contact members 28 and 29.A transformer winding 30 that is adapted to be supplied with currentproportional to the current traversing the secondary winding 21 of thetransformer 19 is disposed on a magnetizable core member 41. Atransformer winding 31, a transformer winding 32 and a transformerwinding 33 are also disposed on the magnetizable core member 41. Thetransformer winding 32 is adapted to be supplied with currentproportional to the current traversing the primary winding 20 of thetransformer 19, and the transformer winding 33 is adapted to be suppliedwith current proportional to the drop in potential across the winding 20of the transformer 19. The windings 30, 31, 32 and 33 are so connectedthat a winding 42, which is also associated with the core member 41 andoperatively connected to the winding 25 of the relay 23, will besupplied with current proportional to the resultant current traversingthe two windings of the transformer 19 compensated by an amountproportional to the iron loss in the transformer 19, as determined bythe transformer winding 33.

The primary winding of a transformer 34 is operatively connected acrossthe terminals of the winding 20 and, the primary Winding of a similartransformer 35 is operatively connected across the terminals of thewinding 21. The secondary windings of the transformers 34 and 35 areconnected in opposition to each other and the circuit, thus constituted,is connected to the winding 26 of the relay 23. A circuit 36, comprisinga reactor 37 a resistor 38 having a substantially constant resistanceand the transformer winding 31, is connected in shunt relation to thewinding 26. Since the secondary windings of the transformers 34 and 35oppose each other, the net or resultant voltage impressed across thewinding 26 represents the voltage loss or drop in the transformer 19. Inother words, the transformers 34 and 35 are so proportioned that theresultant voltage represents the drop in each of the windings in thetransformer 19 reduced to a common voltage. The energy corresponding tothis voltage and the sum of the currents in the primary and second arywindings 20 and 21 is the RI loss plus the iron loss in the transformer19. The current that traverses the circuit 36 is produced by thisvoltage and has a constant phase angular relation therewith. If the lossdue to resistance in the transformer 19 and its iron loss areproportional to the square of the current, the voltage drop will have aconstant phase-angular relation to the current that traverses thewinding 20. Any change in the resistance of the windings 2i) and 21 sochanges the phase-angular re.ation of the voltage drop with respect tothe current that traverses the winding 20 that the phase-angularrelation between the current which traverses the winding 29 and thecurrent which traverses the circuit so must, necessarily, ehai'ige. Asthe phaseangular relation changes, the resultant current or the currentthat traverses the transformer winding 31 changes in sign and,consequently, the armature 27 will be caused to turn in the one or theother direction according to the sign of the current that traverses thetransformer 31. In other words, when the energy loss in the transformer19 exceeds, or bears a predetermined relation to, the energy loss in theresistor 38, the contact member 28 will engage the contact member 29 tocomplete a circuit through the winding 39 of a tripping electromagnet40.

It will be understood that, if the currents traversing the windings 20and 21 are eX- actly 180 out of phase, the one or the other of thetransformer winding 30 and 32 may be omitted. Also, the movable contactmember 28 may be adapted to cooperate with a scale 43 to indicate thetemperature of the transformer 19.

I do not limit my invention to the particular systems illustrated, as itis adaptable to various modifications without departing from the spiritand scope of the invention as set forth in the appended claims.

I claim as my invention:

1. In an electrical system, the combination with a translating deviceand a protective. device, of a resistor having substan tially constantresistance, a relay for controlling the protective device, and means forso connecting the relay to the translating device and the resistor thatit is actuated in accordance with the difference in the energy loss inthe resistor and the translating device.

2. The combination with a translating device and a resistor havingsubstantially constant resistance operatively connected thereto, of anelectro-responsive device, and means for so connecting theelectro-responsive device to the resistor and the translating devicethat it will be actuated in accordance with the diiierence in the energyloss in the resistor and the translating device.

3. The combination with a translating device and a resistor having apredetermined energy loss, of a reverse-energy relay one winding ofwhich is supplied with energy in accordance with the relative diiierencein energy loss in the said resistor and a portion of the translatingdevice.

4;. The combination with a translating device and a resistor, of meansfor determining the ratio of the energy losses in the translating deviceand the resistor, and an electro-responsive device adapted to beactuated when the translating device reaches such temperature that theratio of the energy losses is greater than a predetermined value.

5. In an electric circuit, the combination with a translating device anda resistor connected to the circuit, of a reverse-energy relay onewinding of which is supplied with current proportional to the relativedifference in the currents traversing the resistor and the translatingdevice and the other winding of which is supplied with currentproportional to the voltage impressed across the resistor and thetranslating device.

6. In an electric circuit, the combination with a translating device anda resistor connected to the circuit, of a reverse-energy relay onewinding of which is supplied with current proportional to the relativedifference in the currents traversing the resistor and a portion of thetranslating device and the other winding of which is supplied withcurrent proportional to the voltage impressed across the resistor andthe portion of the translating device.

Copies of this patent may be obtained for 7.-In an electric circuit, thecombination with a translating device, of a resistor the energy loss ofwhich bears a predetermined relation to the energy loss in a portion ofthe translating device, under predetermined conditions, and meansadapted to be actuated when the ratio of the energy loss in that portionof the translating device to the energy loss in the resistor exceeds apredetermined value.

8. In an electric circuit, the combination with a translating device anda resistor, of a reverse-energy relay one winding of which is connectedin parallel relation to the resistor and a portion of the translatingdevice, a transformer one winding of which is supplied with currentproportional to the current traversing the resistor, a second winding ofwhich is supplied with current proportional to the current traversing a.portion of the translating device and a third winding of which is soconnected to the other winding of the relay that only the diflerence inthe currents traversing the resistor and the translating devicetraverses the same.

9. In an electrical system, the combination with a translating deviceand an electroresponsive device, of a resistor having a substantiallyconstant resistance, the energy loss in the said resistor being adaptedto bear a predetermined relation to the energy loss in the translatingdevice, and means for so connecting the electro-responsive device to theresistor and the translating device that the electro-responsive devicewill be actuated in accordance with the relative difference in theenergy loss in the resistor and the translating device.

In testimony whereof, I have hereunto subscribed my name this 24th dayof Oct.

LAURENCE M. PERKINS.

five cents each, by addressing the Commissioner of Patents, Washington,D. C.

